The present invention relates to the sterilization and disinfection arts. It finds particular application in conjunction with sub-critical fluids associated with antimicrobial agents, such as sterilants or disinfectants, for combined cleaning and sterilization or disinfection of medical instruments, equipment, and supplies, and will be described with particular reference thereto. It should be appreciated, however, that the invention is also applicable to the sterilization or disinfection of other items, including food processing equipment and packaging and hospital supplies, such as bed linen and protective clothing, and the like.
The reusability of medical instruments has become increasingly important in an effort to provide cost-effective health care. Many of the instruments that are now sterilized or disinfected, such as endoscopes, contain tortuous paths, narrow lumens, and other difficult to clean areas. Typically, such instruments are cleaned prior to sterilization or disinfection, to remove organic matter and other dirt which impedes the progress of antimicrobial agents to the surfaces of the instruments. Conventional cleaning methods often fail to remove some of the more heavily adhered or inaccessible organic matter, making it difficult for the antimicrobial agent to effectuate complete decontamination of the instruments in a relatively short period of time. Moreover, workers are exposed to the unsterilized, and sometimes poorly cleaned, instruments when transferring the instruments from the cleaning system to a sterilization or disinfection vessel.
Cleaning systems traditionally use solvents which sometimes leave harmful residues on the instruments or which pose environmental hazards. Water-based cleaning compositions, while tending to be less hazardous, often lead to corrosion of metal parts of the instruments with repeated cleaning. Poor water quality sometimes results in deposits on the instruments or to microbiological contamination. Processing time is often lengthy due to the need for drying the instruments between the cleaning and sterilization or disinfection phases.
Recently, supercritical fluid dry cleaning systems have been developed for cleaning instrument parts and as a replacement for chlorofluorocarbons. A supercritical fluid is a pure compound or mixture which is at a temperature and pressure at or above the critical temperature and pressure of the compound. Carbon dioxide is a particularly advantageous fluid because it is a non-polar solvent. This allows cosolvents to be added having a high degree of selectivity. Cleaning is effectuated more rapidly than for many conventional systems, in part because the fluid rapidly evaporates from the cleaned surfaces when the pressure is reduced. EP 0 679 753 A2 discloses a liquid carbon dioxide dry cleaning system which uses agitation and cleaning enhancers, such as surfactants and solvents, to remove contaminants from garments or fabrics.
Supercritical fluid cleaning systems, however, do not necessarily sterilize or disinfect the instruments. To date, such systems have not been used for cleaning medical instruments, and the like. Where sterilization or disinfection, as well as cleaning, is required, a separate sterilization or disinfection process conventionally increases the processing time and poses hazards to workers handling the unsterilized instruments.
Jackson, et al. (U.S. Pat. No. 5,213,619) discloses a supercritical cleaning process in which chemical oxidizing agents, such as hydrogen peroxide, are transported into a cleaning chamber together with a supercritical fluid. The oxidizing agent is exposed to high energy acoustic radiation to create oxidizing radicals within the supercritical fluid. Other additives, such as surfactants, biocides, and the like, may also be included. WO 96/23606 also to Jackson, discloses a centrifugal separation process which removes dirt from contaminated items in a cleaning process which cycles a dense fluid between a pressure below the critical pressure and one above the critical pressure.
However, the high pressures employed in supercritical cleaning call for specialized equipment capable of withstanding the high pressures.
The present invention provides a new and improved combined cleaning and sterilization or disinfection system and process at sub-critical pressures which overcomes the above referenced problems and others.
In accordance with one aspect of the present invention, a method for cleaning contaminants from articles and microbially decontaminating the articles is provided. The method includes contacting the articles with a dense cleaning fluid at a sub-critical pressure to remove contaminants from the articles. The method is characterized by, after the step of contacting the articles with a dense cleaning fluid, contacting the articles with an antimicrobial fluid to microbially decontaminate the articles.
In accordance with another aspect of the present invention, a sub-critical fluid cleaning and microbial decontamination system is provided for combined cleaning of contaminants from medical instruments, and killing microbes on the medical instruments. The system includes a chamber which receives the instruments, a source of a dense cleaning fluid, fluidly connected with the chamber, the dense cleaning fluid being one which is gaseous under ambient conditions. A source of an antimicrobial fluid, separate from the source of the dense cleaning fluid, is fluidly connected with the chamber. An injection system connected with the source of cleaning fluid and with the chamber. The injection system supplies pressurized dense cleaning fluid to the chamber at a pressure sufficient for bringing the dense cleaning fluid within the chamber to a sub-critical pressure and separately supplies the antimicrobial fluid to the chamber.
One advantage of the present invention is that it provides a unitary sterilization or disinfection and cleaning process which reduces processing time.
Another advantage of the present invention is that hazards which would otherwise be posed by microbially contaminated instruments during transfer of the instruments between the cleaning and the decontamination systems are eliminated.
Yet another advantage of the present invention is that it employs cleaning fluids which are amenable to non-hazardous disposal after use, without posing significant environmental hazards.
A further advantage of the present invention is that it enables cleaning fluids and antimicrobial agents to be separately recycled.
A yet further advantage of the present invention is that the processing equipment need not withstand supercritical pressures.
A yet still further advantage of the present invention is that it enables heat sensitive instruments to be cleaned without risk of heat damage.
Still further advantages reside in the ability to clean and microbially decontaminate instruments directly after patient use, without prior drying of the instruments.
Still further advantages of the present invention will become apparent to those of ordinary skill in the art upon reading and understanding the following detailed description of the preferred embodiments.